Engine Cooling problem
1999 BMW 328 6 cyl Two Wheel Drive Automatic
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cooling system signal on

The low coolant warning can be commanded on from the coolant level being too low or from a faulty sensor. If more assistance is required, please repost, and it's okay to go into more detail.

i did replaced the thermostat ,but the car still running hot ,where else can i do ,I'm desperad ,if is a sensor wich one ,is one inside the tank ,is that a sensor?
can a sensor create the cooling problem,I replaced the extended tank because it has a big crack along of it ,i don't think coolent is getting in the motor ,where else is out there other than the sensor,or the sensor the problem?

When you replaced the thermostat, did you purge all the air from the system? There is a black plastic screw on the expansion tank that needs to be either loosened or removed during the filling of the cooling system. Do that and let me know if the problem still exists.